The present invention relates to an aerodynamic fairing apparatus, and more particularly to an aerodynamic fairing apparatus connectable to external bodies on a flight vehicle which is specially configured to reduce convergent flow between bodies as well as reduce flow separation and reattachment.
Rocket motors are currently widely employed for a number of uses in the world of aviation and astronautics. These uses may include launching payloads into space as part of a spacecraft, or as the propulsion source of a launch vehicle. Rocket engines are generally of two types. The first type is a liquid rocket engine which uses one or more propellants, mixes them, and then burns the fuel in a combustion chamber. Liquid rocket engines provide a large amount of thrust per pound, and are typically employed in all launch vehicles that are employed in manned space flight. Liquid rocket engines are in some cases designed for varying amounts of thrust and in some cases may be shut off and subsequently restarted.
A second type of rocket engine is a solid rocket motor (SRM). This type of engine burns a solid propellant inside a pressure tube. The solid propellant has both fuel and oxidizer mixed together and that fuel may be burned from the end up, or more commonly from the center outward. Once started a solid rocket motor cannot be shut off until it burns itself out. These types of motors are most commonly used as the propulsion source for missiles because they can be used quickly and without delay.
Recently the number of payloads which are being launched into space has increased. As the weight of the payloads and the height of the desired orbits has increased (for example, geosynchronous orbit) the benefits of liquid and solid rocket motors have been combined in providing high-powered launch vehicles. In one configuration, one or more solid rocket motors may be attached to the external surface of a launch vehicle and/or liquid rocket motor. The solid rocket motors provide for the lift off and initial propulsion of the vehicle to a desired staging altitude where the liquid rocket motor is then employed for a controlled flight into orbit.
The inventors have recognized that when strap on rocket motors are employed in conjunction with a flight vehicle, the aerodynamic shape of the strap on rocket motor while traveling at high speeds may generate aero-acoustic effects with regard to the launch vehicle, other strap on rocket motors and any enclosures on the exterior of the launch vehicle. As such, the inventors have identified an aerodynamic fairing configuration for use on strap on rocket motors which reduces aero-acoustic (vibrational and turbulence) effects with regards to the launch vehicle and other bodies mounted in close proximity.
Described herein is a aerodynamic fairing which is configurable to be mounted on a substantially cylindrical body such as a strap on rocket motor, which in turn is mounted and employable on a launch vehicle such as a liquid fueled rocket. The aerodynamic fairing is shaped such that convergent flow between the strap on rocket motor and the launch vehicle is significantly reduced. Further, other surfaces of the fairing are configured to direct air flow in a desired direction and are shaped such that a smooth transition is created between the fairing and the strap on rocket motor to avoid the separation and reattachment of airflow.
In one configuration of the invention, the aerodynamic fairing is connectable to another body. The aerodynamic fairing which is mountable hereon is configured with a leading edge which is substantially straight and has a width which is substantially equal to the diameter of the strap on rocket motor. The leading edge is a intersection between the radially inboard and radially outboard surfaces of the aerodynamic fairing. The radially inboard surface of the aerodynamic fairing is configured such that beginning at the leading edge, it is substantially flat and straight going aft, and is configured to transition from the flat shape to a cylindrical shape at the base end. The radially outboard surface is shaped such that it includes a circular arc of large radius. This radius is defined to generate a surface that intersects the leading edge and connects to the aft cylinder without slope discontinuity. As with the radially inboard surface, the radially outboard surface transitions from an edge to the cylindrical shape of the strap on rocket motor at the base end. The base end includes a circular cross-section such that the fairing may be connected to the strap on rocket motor.
The body to which the fairing is connectable may be cylindrical in shape. In yet another configuration of the invention the cylindrical body may be an strap on rocket motor. The fairing may be configured such that a shoulderless configuration is provided when the fairing is mounted on the strap on rocket motor. The fairing may further include a cylindrical portion which provides for mounting the fairing on the strap on rocket motor.
The strap on rocket motor with the fairing mounted thereon may be connectable to a core body such as a launch vehicle. The launch vehicle may be at least partially configured as a liquid rocket motor. The strap on rocket motor and fairing may be connectable to the launch vehicle such that the inboard surface of the fairing is in closest proximity to the core body. The strap on rocket motor and fairing combination may also be mounted on the launch vehicle in close proximity to other bodies mounted on the launch vehicle. These other bodies may include other strap on rocket motor""s or enclosures on the exterior of the core body. These enclosures may be employed to house various equipment for the launch vehicle such as electronics.
In yet another configuration of the invention, the aerodynamic fairing described herein may include a base end which is configured to be connectable to a cylindrical body. The base end may include a substantially circular cross section defined by a plurality of azimuthal reference points defining longitude located along a perimeter of the circular cross section extending from a most inboard point on the circular cross section to a most outboard point.
Extending from the base end may be a body portion of the fairing which includes an exterior surface definable by a plurality of traces each of which extend from one of the plurality of longitudinal reference points forward from the base end. The traces are measured in planes parallel to a centerline for the cylindrical body and perpendicular to an inboard reference plane. In defining the shape of the aerodynamic fairing, the intersection of the traces with the inboard reference plane define a leading edge portion for the fairing. Further, each of the traces define an arc, wherein the measured radius for the arcs increase from a minimum measured radius at the most outboard point of the fairing to a maximum radius measured at a most inboard point.
In yet another configuration of the invention the trace measured along the most inboard point is substantially flat. When the fairing is connected to a cylindrical strap on rocket motor and mounted on a launch vehicle, the fairing is oriented such that the most inboard point is in closest proximity to the launch vehicle.